STUDIES ON STROKE-PRONE SHR(SHRSP): (1) All SHRSP were autopsied after natural death and incidence of stroke in the recent offspring was confirmed to be constantly higher than 80%. (2) Various characteristics of SHRSP were analyzed. (1) Signs and symptoms were studied neurologically and herniation was found to be important in the terminal stage. (2) Physico-chemical characteristics of arterial walls in SHRSP were proven to be different in the elastic module, acid mucopolysaccharide content and amino acid constituents of collagen and elastin. (3) Regional cerebral blood flow(rCBF) was clearly decreased in SHRSP with blood pressure higher than 200 mmHg and such reduction preceded the development of vascular lesions. (4) Plasma renin content was increased in SHRSP with vascular lesions and molecular forms of renin were different in SHR. (3) A back cross between SHR and normotensive rats was repeated to obtain "normotensive" SHR with blood pressure less than 150 mmHg. (4) Control of blood pressure under 200 mmHg kept rCBF within normal range, which was proven to be important for prophylaxis of stroke. (5) Environmental factors such as nutrition greatly affected the incidence of stroke: a low protein diet with increased salt intake was worst, while a high protein diet decreased the incidence even under salt loading. STUDIES ON OTHER HYPERTENSIVE SEQUELAE IN SHR: A new selectively-bred substrain of SHR was confirmed to be a good model for studies on atherogenesis. When fed on a hypercholesterolemic diet, they developed arterial fat deposits within a few weeks not only in systemic arteries such as mesenteric and renal arteries but also in cerebral arteries which were generally regarded as being resistant to fat deposition. Importance of hypertension in the fat deposition of cerebral arteries, the initiation process of cerebral arteriosclerosis, was confirmed in this model, while coronaries were found to be rather resistant to hypertension-induced arterial fat deposition. The initiation mechanisms of acute arterial fat deposition was further analyzed and vascular functions such as vasoconstriction and dilatation were closely related to increased permeability which resulted in acute fat deposition.